Collaborative Research: An Empirical Blueprint for the Gravitational-Wave Background

Orbiting supermassive black holes in the centers of galaxies are thought to produce very low frequency gravitational waves that could be detected by careful timing of the arrival of radio pulses from pulsars through the ongoing pulsar timing array project. It is expected that the combined signals from many of these systems will produce a background noise that may soon be detectable by pulsar timing arrays.

This project will use a new method based on observations of accreting supermassive black holes to provide an estimate of the strength of this background noise as well as it's distribution in gravitational wave frequencies. The project will use this new method to provide a framework for determining the history of the growth of supermassive black holes once the background noise is detected.

The project will also create a Pulsar Search Collaboratory hub in New Jersey and New York that will involve high school students in the search for pulsars using real data. This award advances the goals of the Windows on the Universe Big Idea.

The project will use observations of quasar luminosity functions at different redshifts combined with local observations of dual Active Galactic Nuclei to build an empirically-based model of the cosmological distribution of supermassive black hole binaries that will contribute to the stochastic gravitational wave background expected to be detected in pulsar timing array observation. This approach is complementary to the existing approach that is based on galaxy merger simulations.

The new approach will determine key physical parameters that can be constrained through detection of the gravitational wave background. The project will also create a Pulsar Search Collaboratory hub in New Jersey and New York. The Pulsar Search Collaboratory is a long-standing NSF supported program that allows high schools students to search for pulsars with real radio data. It is a low-barrier way for students to experience science and scientific discovery.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.